In general, the term “tissue handling procedure” can be used to describe procedures for preparing tissue samples for microscopic examination and, traditionally, comprises embedding the tissue sample in paraffin wax and sectioning the paraffin-embedded tissue sample very thinly with a microtome. Thereafter, the thin sections may be floated onto glass slides, stained and finally coverslipped for microscopic examination. In histopathology, not only are the size and shape of the cells considered, but also the tissue structure. It is therefore useful to orient the tissue properly so that the plane of cutting by the microtome produces a cross section of tissue suitable for examination. Prior to embedding, the tissue sample may undergo tissue processing in a tissue processor, in which the sample is processed with various fluid materials appropriate to assist in preparing the sample for the examination. In a typical tissue processing operation the tissue sample may be fixed, dehydrated, cleared, and then infiltrated with molten paraffin wax. Then, depending on the examination to be conducted and subsequent to embedding and sectioning, the tissue sample may be stained for a particular analysis methodology. The fluid materials used in tissue processing steps may comprise formaldehyde, alcohol, xylene or other solvents, and paraffin wax. In recent developments being the subject of co-pending patent applications by the present applicant, xylene-free processing is now possible.
Therefore, the term “tissue handling procedure” is used herein to refer to any one of the abovementioned procedures that are performed in preparing tissue samples for examination.
A histology laboratory processes a number of tissue samples for examination and it is important that the tissue samples be prepared as efficiently as possible.
For example, U.S. Pat. No. 3,674,396 to McCormick discloses cassettes in which a tissue sample is both prepared for embedding through exposure to various solutions and is then embedded in proximity to the cassette. The '396 McCormick patent discloses a process wherein the tissue sample is statically exposed to the various fluids required for preparation of the tissue samples. In the cassettes of the '396 McCormick patent, perforated walls are used to enclose the tissue samples while providing access to the tissue samples for the various solutions and finally to molten paraffin wax. After subjecting the tissue sample to the various tissue processing fluids, molten embedding material may be poured into the well of a mold. The treated tissue sample may then be removed from the cassette and oriented in a specific manner in the embedding material in the well of the mold. Typically the mold is then placed onto a cold surface to harden the bottom layer of embedding material to ensure the tissue stays in the correct orientation, before applying further embedding material to fully embed the tissue. Additional molten embedding material is then poured over the tissue sample. The cassette used to process the tissue sample is then placed over the well in the mold and additional molten embedding material is poured into the cassette. After the embedding material solidifies, a cast block is formed that comprises the cassette as its base and a protruding portion having the tissue specimen disposed adjacent its front surface. The size of various cassettes, which have been developed for processing tissue samples, has been relatively standardized so that the cassette may be used, inter alia, to clamp the block into a microtome for sectioning. U.S. Pat. No. 5,080,869 to McCormick describes a typical cassette presently used for processing tissue samples. The cassette of the '869 McCormick patent is stackable and may be used for preparing a plurality of specimens. The cassette generally comprises a plurality of apertures disposed in the walls of the cassette for passage of processing fluids in a direction both orthogonal and parallel to the plane of the bottom wall of the cassette. The cassette also comprises a sloping extension of the front wall of the cassette for ease in placing indicia on the cassette for identification of the sample.
In the majority of histology laboratories, tissue samples are processed in a cassette that has come to be manufactured in accordance with at least one de facto industry standard, for example, along the lines of the above noted '396 McCormick patent and thereafter the above noted '869 McCormick patent. One cassette is typically used per tissue sample in order to ensure samples may be uniquely identified and labelled to ensure accurate diagnosis. For diagnostic reasons samples may vary greatly in size, from samples that almost fill a cassette completely to small biopsies that may be less than 1 mm in diameter. With respect to prior art tissue cassettes, the tissue specimen is held loosely and individually in a cassette to segregate it from other samples. After tissue processing, the next step is usually embedding the tissue sample in paraffin wax. The embedding procedure typically comprises the following steps:                Specimen is taken out of the cassette at some time after tissue processing is completed;        The histologist selects the correct size mold to use;        A small volume of wax is dispensed to the bottom of the mold;        The tissue specimen is placed into the mold and orientated carefully by the laboratory technician using wax to orient the tissue;        A holding fixture for the microtome (ordinarily a portion of a tissue cassette) is placed on the top of the mold. The fixture also provides an identification label;        Additional wax is dispensed by the technician to attach the fixture to the tissue sample, now enclosed in a block of wax;        The wax block is then cooled and solidified;        The wax block is then removed from the mold and ready to be mounted on the microtome via the fixture for sectioning.        
The above procedure requires the histologist to spend time removing the tissue from the cassette after tissue processing and then orienting the samples in wax in their own mold.
Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art on or before the priority date of the invention disclosed herein or, any claims defined herein.